Helium coolant

High operating temperatures al moderate pressures are achieved through the use of helium as the coolant. Helium is attractive as a coolant because it (1) is chemically inert (2) absorbs essentially no neutrons and (3) makes no contributions to the reactivity of the system. Carbon dioxide also has been used as a coolant. 

Figure 3 briefly shows the structure, major specification and the history of the HTTR R D by JAEA. The reactor core is composed of graphite prismatic blocks. Fuels are inserted in the blocks as a shape of cylindrical graphite compacts in which tri-isotropic (TRISO)-coated fuel particles with U02 kernel are dispersed. The coolant helium gas of the HTTR is circulated at 4 MPa to an intermediate heat exchanger where high temperature heat is transferred to hydrogen production process. 

The LS-VHTR uses the same type of coated-particle graphite-matrix fuel that has been successfully used in high-temperature gas-cooled reactors such as the Peach Bottom Reactor, the Fort St. Viain Reactor (FSVR), the Arbeitsgemeinshaft Versuchsreaktor (AVR), and the Thorium High-Temperature Reactor (THTR). At this time, graphite-based fuels have been demonstrated to be compatible with only two coolants helium and fluoride salts. 

As for the coolant, helium, a chemically inactive gas, is used. It is compatible with the structural material and graphite, and it contributes to the reactor s high-temperature features. 

NEUTRAl BEAM INJECTOR S TURBINE BUILDING REACTOR COOLANT helium ... 

Primary Coolant Helium Helium Lithium Helium Helium Lithium Helium Helium... 

The PBMR functions as a direct Brayton cycle, with primary coolant helium flowing downward through the core and exiting at 900°C. The helium then enters the turbine relinquishing energy to drive the electric generator and compressors. 

Gas-cooled fast reactor or high temperature reactor NPP (reactor coolant — helium P = 9 MPa and Pin/Pont = 49(V850°C primary power cycle — direct Brayton gas turbine cycle possible backup — indirect Rankine steam cycle). >50... 

Table 26.1 Impurity content in the coolant helium of experimental reactors and composition of some standard test gases...

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